WO2021224303A2

WO2021224303A2 - Polyethylene-type materials, the solvolysis thereof and production of finished parts therefrom

Info

Publication number: WO2021224303A2
Application number: PCT/EP2021/061801
Authority: WO
Inventors: Stefan Mecking; Manuel Häußler; Marcel Eck
Original assignee: Universität Konstanz
Priority date: 2020-05-06
Filing date: 2021-05-05
Publication date: 2021-11-11
Also published as: WO2021224303A3; EP4146730A2; EP3907250A1

Abstract

According to a first aspect, the invention relates to a polyethylene-type polymer comprising methylene groups (CH₂) and at least one functional group selected from group O-C(=O) and group O-C(=O)-O, the polyethylene-type polymer having a number-average molecular weight (Mn) in the range of 20,000 to 10,000,000 g/mol. In a second aspect, the invention relates to a method for producing specific monomers of general formula (II) and/or specific oligomers of general formula (III). In a third aspect, the invention relates to a composition comprising a monomer of general formula (II) and/or an oligomer of general formula (III), the composition being obtained or obtainable by means of the method of the second aspect. A fourth aspect of the invention relates to the use of the composition according to the third aspect to produce polymers. A fifth aspect of the invention relates to a method for producing a finished part, comprising: - provision of a material having a polyethylene-type polymer; and - primary forming of the material. A sixth aspect of the invention relates to a method for producing a finished part from a material, the material having a polyethylene-type polymer, wherein the finished part is produced by means of an additive manufacturing method.

Description

Polyethylene-like materials, their solvolysis and manufacture of prefabricated parts from them

According to a first aspect, the invention relates to a polyethylene-like polymer comprising methylene groups (CH2) and at least one functional group selected from the 0-C (= 0) group and the 0-C (= 0) -0 group, the polyethylene like polymer has a number average molecular weight (M _n ) in the range from 20,000 to 10,000,000 g / mol. In a second aspect, the invention relates to a process for the preparation of specific monomers of the general formula (II) and / or specific oligomers of the general formula (III). In a third aspect, the invention relates to a composition comprising a monomer of the general formula (II) and / or an oligomer of the general formula (III), the composition being obtained or obtainable by the process of the second aspect. A fourth aspect of the invention relates to the use of the composition according to the third aspect for the production of polymers. A fifth aspect of the invention relates to a method for producing a prefabricated part, comprising providing a material which has a polyethylene-like polymer, and molding the material into the original. A sixth aspect of the invention relates to a method for producing a finished part from a material, the material comprising a polyethylene-like polymer, the finished part being produced by means of an additive manufacturing process.

The production and processing quantities in the plastics industry have increased almost explosively in the last few decades, with plastics mostly being made from organic materials such as cellulose, coal, natural gas and crude oil. The spectrum of polymers produced is diverse and includes various thermosets and thermoplastics. The thermoplastics include, for example, polyolefins such as polyethylene (PE) and polypropylene (PP), polyvinyl chloride (PVC), polyesters such as polyethylene terephthalate (PET), polystyrene and expanded polystyrene (PS / PS-E). A large part of the plastics produced are made up of polyethylene, polypropylene and polystyrene. This group is therefore of great relevance, also with regard to waste management, if you consider that polyolefins such as polyethylene and polypropylene are the main material for plastic packaging and containers, which have a very short service life compared to other polymer products.

With regard to the mass of waste, which represents an environmental problem due to the lack of degradability, and the immense resources contained in this waste, recycling of plastics is a central aspect.

Closed recycling of plastics is particularly desirable. One approach is to reuse the plastics as such, also known as “mechanical recycling”. This goes hand in hand with a greatly reduced quality of the recycled materials. The reasons are the loss of molecular weight and other material properties due to the mechanical and thermal treatment steps, but in particular the contamination with other types and qualities of plastics in the recycling of typical plastic waste streams. Therefore, there is a chemical breakdown into low molecular weight building blocks, so-called oligomers and in particular monomers, which serve as the starting material for a renewed polymerization can be a desirable approach to obtaining high quality materials (commonly referred to as “chemical recycling”). Chemical recycling processes are the subject of research: In chemical recycling, the polymers are usually separated into shorter oligomeric units or even monomers through the action of heat, catalysts and solvents. The oligomers and monomers obtained in this way can then be used again for plastics production, which saves primary resources. Various processes using solvolysis and / or pyrolysis, with and without a catalyst, have already been described. For example, US Pat. No. 6,472,557 B1 discloses a recycling process in which PET with zinc acetate in methanolic solution is heated under autogenous pressure in an autoclave.

In the case of polyolefins, in particular polyethylene, the previously known chemical recycling is associated with limited yields of ethylene monomer of <50%. Furthermore, a lot of energy is required, since the process requires temperatures of approx. 700 ° C.

Polyethylene-like materials made from unsaturated fatty acids have become known in recent years. For example, DE 102016010503 A1 describes a method based on chain multiplication of unsaturated fatty acids. Long-chain aliphatic polyesters based on vegetable oils are described by Stempfle et al. (F. Stempfle, B. S. Ritter, R. Mülhaupt, S. Mecking, Green Chem., 2014, 16, 2008-2014).

Ortmann et al. describe the hydrolytic degradability of polyethylene-like polyacetals and polycarbonates (P. Ortmann, I. Heckler, S. Mecking, Green Chem., 2014, 16, 1816-1827). Experiments on hydrolytic degradation were carried out on solids in concentrated or dilute, in each case acidic or basic aqueous media, the focus being on the degradation of the polymers, but not on the recovery of the monomers used for their production.

The object of the present invention was therefore to provide polyethylene-like materials and an associated process which enables the monomers to be recovered as completely as possible from the polyethylene-like materials by solvolysis or a closed loop as possible for the recovery and renewed polymerisation of such monomers. The polyethylene-like materials should have good degradability in the solvolysis process.

In the following, the terms “have”, “have”, “comprise” or “include” or any grammatical deviations therefrom are used in a non-exclusive manner. Accordingly, these terms can relate to situations in which, apart from the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the expression "A has B", "A has B," A comprises B "or" A includes B "can refer to the situation in which, apart from B, no further element is present in A ( ie on a situation in which A consists exclusively of B), as well as on the situation in which, in addition to B, there are one or more other elements in A, for example element C, elements C and D or even further elements.

It is also pointed out that the terms “at least one” and “one or more” as well as grammatical modifications of these terms, if they are used in connection with one or more elements or features and are intended to express that the element or feature is provided once or several times can be used, as a rule, only once, for example when the feature or element is introduced for the first time. If the feature or element is subsequently mentioned again, the corresponding term “at least one” or “one or more” is generally no longer used, without this limiting the possibility that the feature or element can be provided once or several times.

Furthermore, the terms “preferably”, “in particular”, “for example” or similar terms are used below in connection with optional features, without this limiting alternative embodiments. Features introduced by these terms are optional features, and it is not intended to use these features to restrict the scope of protection of the claims and in particular of the independent claims. Thus, as the person skilled in the art will recognize, the invention can also be carried out using other configurations. In a similar way, features which are introduced by “in an embodiment of the invention” or by “in an exemplary embodiment of the invention” are understood as optional features, without this being intended to limit alternative configurations or the scope of protection of the independent claims. Furthermore, these introductory expressions are intended to leave unaffected all possibilities of combining the features introduced thereby with other features, be they optional or non-optional features.

1 . Aspect - polyethylene-like polymer

According to a first aspect, the invention relates to a polyethylene-like polymer comprising methylene groups (CFI2) and at least one functional group selected from the 0-C (= 0) group and the 0-C (= 0) -0 group, the polyethylene like polymer has a number average molecular weight (M _n ) in the range from 20,000 to 10,000,000 g / mol.

The number average molecular weight M _n is determined by means of gel permeation chromatography (GPC) against polystyrene standards in the range of 400-5,000,000 g / mol (universal calibration).

Preferably 90 to 99.5 mol%, more preferably 92 to 98 mol%, of the polyethylene-like polymer consist of methylene units (CFI2).

The term “polyethylene-like polymer” is common to those skilled in the art for such polymers (see, for example, Ortmann et al. (P. Ortmann, I. Fleckler, S. Mecking, Green Chem., 2014, 16, 1816-1827). The polymers according to the invention have a solid-state structure as in the case of linear high-density polyethylene (HDPE), so in particular they have the same wide-angle X-ray scattering (WAXS) as HDPE. Furthermore, the polymers of the present invention have the same degrees of crystallinity as HDPE, preferably at least 60% from WAXS. For comparison: According to the literature, low-density polyethylene (LDPE) only has a degree of crystallinity of approx. 40% (Jeremic, D .: Polyethylene. In Ullmann's Encydopedia of Industrial ChemistryW \\ e - \ IC, 2012). The polymers of the present invention likewise have tensile elongation properties similar to those of HDPE, and the modulus of elasticity E _y , which is in the range from 650 to 1100 MPa, and the _{elongation at elongation a y} , which is in the range from 15 to 22 MPa, are comparable as with HDPE (E _y approx. 1000 MPa, a _y approx. 19 MPa). For comparison: According to the literature, LDPE only has a modulus of elasticity of E _y = 240 MPa, and an _{elongation at yield of a y} = 12 MPa (Jeremic, D .: Polyethylene. In Ullmann's Encydopedia of Industrial Chemistry W \\ e \ / AICY \ , 2012).

According to a preferred embodiment of the polyethylene-like polymer, this has a repeating unit of the general formula (I)

[-X- (CH ₂ ) a-]

(I) on, where

X is selected from C (= 0) -0- group or -0-C (= 0) -group and-0-C (= 0) -0- group; a is an integer from 8 to 200. In a preferred embodiment, the general formula (I) is as follows: [-X- (CH ₂ ) _a -] _n , where X ”and“ a ”have the meaning given.

The index "a" can be the same or different for each of the n repetition units, i.e. with n repetition units there is a maximum of n different values for the index "a". "X" can be the same or different for each of the n repeating units, ie each of the n X groups is independently selected from C (= 0) -0-group or -0-C (= 0) -group and -0- C (= 0) -0 group.

The index “n”, which is given for the repeating unit of the general formula (I), preferably stands for an integer from the range from 8 to 60,000 (90 to 99.5 mol% methylene groups in the polymer), more preferably from the range from 28 up to 47,000 (92 to 98 mol% methylene groups in the polymer).

According to a further preferred embodiment of the polyethylene-like polymer, this has a repeating unit of the general formula I (la)

[X ¹ - (CH ₂ ) a-] n

(la) on, where X ^{1 is} selected from C (= 0) -0- group and -0-C (= 0) -group; a is an integer from 8 to 200.

Polyethylene-like polymers having a repeating unit of the general formula I (la) are also referred to as “polyesters”. The index “a” can be the same or different for each of the n repeating units of the general formula (Ia), ie with n repeating units there is a maximum of n different values for the index “a”. "X ¹ " can be the same or different for each of the n repeating units, ie each of the n X ¹ groups is independently selected from C (= 0) -0-group and -0-C (= 0) -group.

The index “n”, which is given for the repeating unit of the general formula (Ia), stands for an integer from the range from 8 to 60,000, preferably from the range from 8 to 58,562 - this corresponds to an M _n in the range of 20,000 to 10,000,000 g / mol a percentage of 90-99.5 mol% methylene groups in the polymer, corresponding to 8-200 methylene groups per functional group in (la). In a further preferred embodiment, n stands for an integer from the range from 18 to 60,000, preferably from the range from 18 to 58,562 - with an M _n in the range from 50,000 to 10,000,000 g / mol, this corresponds to a percentage of 90 - 99.5 mol% methylene groups in the polymer.

More preferably, n in (Ia) stands for an integer from the range from 28 to 47,000, more preferably from the range from 28 to 46,984 - this corresponds to _{a percentage of with an M n} in the range from 20,000 to 10,000,000 g / mol 92-98 mol% methylene groups in the polymer, corresponding to 12-49 methylene groups per functional group in (la). In a further preferred embodiment, n stands for an integer from the range from 70 to 47,000, more preferably from the range from 70 to 46,984 - this corresponds to _{a percentage of 92 for an M n} in the range from 50,000 to 10,000,000 g / mol - 98 mol% of methylene groups in the polymer. For polyethylene-like polymers having a repeating unit of the general formula (Ia), it is preferred that the number average molecular weight is in the range from 50,000 to 10,000,000 g / mol.

According to an alternative, further preferred embodiment of the polyethylene-like polymer, this has a repeating unit of the general formula (Ib)

[-0-C (= 0) -0- _(CH2) a-] n

(Ib), where a is an integer from the range 8 to 200.

Polyethylene-like polymers having a repeating unit of the general formula I (Ib) are also referred to as “polycarbonates”. The index “a” can be the same or different for each of the n repeating units of the general formula (Ib), ie with n repeating units there is a maximum of n different values for the index “a”. The index “n”, which is given for the repeating unit of the general formula (Ib), stands for a whole Number from the range from 8 to 60,000, preferably from the range from 8 to 53,546 - with an M _n in the range from 20,000 to 10,000,000 g / mol, this corresponds to a percentage of 90 - 99.5 mol% methylene groups in the polymer, corresponding to 8 - 200 methylene groups per functional group in (Ib). More preferably, n in (Ib) stands for an integer from the range from 28 to 47,000, more preferably from the range from 28 to 43,698 - with an M _n in the range from 20,000 to 10,000,000 g / mol this corresponds to a percentage of 92-98 mol% methylene groups, corresponding to 12-49 methylene groups per functional group in (Ib). For polyethylene-like polymers having a repeating unit of the general formula (Ib) it is preferred that the number average molecular weight is in the range from 20,000 to 10,000,000 g / mol.

2nd aspect - solvolysis process

According to a second aspect, the present invention relates to a process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III)

Y ¹ - (CH ₂ ) CY ²

(II) where Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) group or -C (= 0) -0-R group and OH group, where R is a hydrogen atom or a C1-C10-alkyl group, preferably a hydrogen atom or a C1-C5-alkyl group, more preferably a hydrogen atom or a C1- or C2-alkyl group; where the radicals Y ¹ , Y ^{2 are} preferably each the same, and the index c is an integer from the range 8 to 200,

Y ¹ - [(CH ₂ ) aX-] mY ²

(III) where Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) -0- group and -0-C (= 0) -0-R- group, R-0-C (= 0) group or -C (= 0) -0-R group and OH group, where R is a hydrogen atom or a C1-C10-alkyl group, preferably a hydrogen atom or a C1-C5-alkyl group, more preferably is a hydrogen atom or a C1 or C2 alkyl group; X is selected from the C (= 0) -0 group or -0-C (= 0) group and -0-C (= 0) -0 group, where X is in the last repeating unit of formula (III) , ie when transitioning to Y ² , does not exist; a is an integer from the range 8 to 200; and the subscript m is an integer from the range 2 to 40; wherein the method comprises: i) producing an alcoholic and / or aqueous mixture of a polyethylene-like polymer comprising methylene groups and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group ; ii) heating the mixture provided according to i), preferably under autogenous pressure, to a temperature in the range from 20 to 400 ° C., preferably from 60 to 250 ° C., more preferably from 80 to 180 ° C .; iii) Separating the monomers of the general formula (II) and / or oligomers of the general formula (III) from or from the alcoholic and / or aqueous mixture obtained according to ii).

The index "a" can be the same or different for each of the m repeating units of the general formula (III), i.e. with m repeating units there are a maximum of m different values for the index "a". "X" can be the same or different for each of the n repeating units, ie each of the m X groups is independently selected from C (= 0) -0 group or -0-C (= 0) group and -0- C (= 0) -0 group.

X is not present in the last repeating unit in the oligomers of the general formula (III). This means, for example for m = 2, the following structure of an oligomer of the general formula (III):

Y ¹ - [(CH ₂ ) aX -] - [(CH ₂ ) a -] - Y ²

The structure for oligomers of the general formula (III) with m in the range from 3 to 40 is analogous.

The process described above is also referred to as the “solvolysis process”. As described at the beginning, many known recycling processes have various disadvantages: With chemical recycling, it is often disadvantageous that the monomers used can only be recovered from the plastic in poor yields or that various other degradation products result from side reactions, etc., which then again interfere with a renewed polymerization. Furthermore, the recovery of ethene from polyethylene, for example, requires a high level of energy expenditure, since temperatures of approx. 700 ° C are required.

For the solvolysis process according to the invention, it could surprisingly be shown that recovery of monomers and / or oligomers from the polyethylene-like polymer is possible under significantly milder conditions, including temperatures well below 700 ° C., and that furthermore only a low energy expenditure is required. In addition, the monomers and / or oligomers are obtained in high selectivities and in high quality. Even dyes and other constituents that are added to the polyethylene-like polymer can be separated without any problems. Other polymers such as, for example, polyolefins, in particular polypropylene or polyethylene, can also be separated quantitatively. These other polymers, in particular polyolefins, are present unchanged in polymeric form after the solvolysis stage (ii) has taken place, in addition to the monomers of the general formula (II) and / or oligomers of the general formula (III). The monomers of the general formula (II) and / or oligomers of the general formula (III) can be separated off in a simple way from these substances, which are present unchanged in polymeric form. The solvolysis process according to the invention enables multi-cycle recycling to be carried out, ie several rounds of polymerization of monomers, solvolysis and renewed polymerization of the monomers and / or oligomers obtained, etc. are possible. In other words, so-called “closed-loop recycling” is possible.

The term alcoholic and / or aqueous mixture according to (i) includes solutions and heterogeneous mixtures of alcohol and / or water with the polyethylene-like polymer. Analogously, it applies to the alcoholic and / or aqueous mixtures obtained according to ii) that they comprise solutions and heterogeneous mixtures of alcohol and / or water with the monomers of the general formula (II) and / or oligomers of the general formula (III).

The polyethylene-like polymer used for the process has a number average molecular weight (M _n ) in the range from 5,000 to 10,000,000 g / mol, preferably in the range from 10,000 to 10,000,000 g / mol. In preferred embodiments, it has a number average molecular weight (M _n ) in the range from 20,000 to 10,000,000 g / mol or in the range from 50,000 to 10,000,000 g / mol.

M _n is also determined in the context of the second aspect of the invention by means of gel permeation chromatography (GPC) against polystyrene standards in the range from 400-5,000,000 g / mol (universal calibration).

The process preferably further comprises: iv) optional purification of the monomers of the general formula (II) and / or oligomers of the general formula (III) obtained in accordance with iii); v) Repolymerization of the monomers of the general formula (II) and / or oligomers of the general formula (III) obtained according to iii) or iv) to give a polymer, preferably a polyethylene-like polymer.

Such a solvolysis process comprising step (v) represents closed recycling, wherein after step (v) a polymer is present which is equivalent to a polymer produced directly from the appropriate monomers, ie there is no deterioration in the mechanical and chemical properties of the material .

In a preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III), the polyethylene-like polymer comprises methylene groups and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group, a repeating unit of the general formula (I)

[-X- (CH ₂ ) a-]

(l), where

X is selected from C (= 0) -0- group or -0-C (= 0) -group and-0-C (= 0) -0- group; a is an integer from 8 to 200. In a preferred embodiment, the general formula (I) is as follows: [-X- (CH ₂ ) _a -] n, where X ”and“ a ”have the meaning given.

The index "a" can be the same or different for each of the n repeating units of the general formula (I), i.e. with n repeating units there is a maximum of n different values for the index "a". X ”can be the same or different for each of the n repeating units, ie each of the n X groups is independently selected from C (= 0) -0-group or -0-C (= 0) -group and-0-C (= 0) -0 group. The index “n” for the repeating unit of the general formula

(I) is an integer from the range from 2 to 60,000 (90 to 99.5 mol% of methylene groups in the polymer with an M _n in the range from 5,000 to 10,000,000 g / mol). More preferably n stands for an integer from the range from 4 to 60,000 (90 to 99.5 mol% of methylene groups in the polymer with an M _n in the range from 10,000 to 10,000,000 g / mol), more preferably n stands for an integer the range from 8 to 60,000 (90 to 99.5 mol% of methylene groups in the polymer with an M _n in the range from 20,000 to 10,000,000 g / mol), more preferably n is an integer from the range from 18 to 60,000 (90 to 99.5 mol% of methylene groups in the polymer with an M _n in the range from 50,000 to 10,000,000 g / mol).

N is preferably an integer from the range from 8 to 47,000 (92 to 98 mol% of methylene groups in the polymer with an M _n in the range from 5,000 to 10,000,000 g / mol), more preferably from the range from 14 to 47,000 ( 92 to 98 mol% of methylene groups in the polymer with an M _n in the range from 10,000 to 10,000,000 g / mol), more preferably in the range from 28 to 47,000 (92 to 98 mol% of methylene groups in the polymer with an M _n in the range of 20,000 to 10,000,000 g / mol), more preferably from the range from 68 to 47,000 (92 to 98 mol% of methylene groups in the polymer with an M _n in the range from 50,000 to 10,000,000 g / mol).

Preferably in the context of the process for the preparation of monomers of the general formula

(II) and / or oligomers of the general formula (III) as described above is that the alcohol is selected from the group of monofunctional or polyfunctional C1 -C10 alcohols and mixtures thereof, the alcohol preferably one or more alcohols of the formula R-OFI comprises, where the radical R is a C1-C10-alkyl group, preferably a C1-C5-alkyl group, more preferably a C1- or C2-alkyl group; wherein the alcohol more preferably comprises methanol.

In a preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) as described above, water is used to produce the mixture according to (i).

In a further preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III), an alcoholic mixture is used, the alcoholic mixture of the polyethylene-like polymer according to i) having a water content in the range of 0 to 5% by weight, preferably in the range from 0 to 1% by weight, more preferably in the range from 0 to 0.55% by weight, more preferably of in the range from 0 to 0.1% by weight, based on the total weight of the alcoholic mixture.

In a preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) as described above, the alcoholic and / or aqueous mixture of the polyethylene-like polymer according to i) comprises in the range from 0 to 20% by weight, preferably in the range from 0 to 15% by weight, more preferably in the range from 0 to 10% by weight, based in each case on the weight of the polyethylene-like polymer used, of a catalyst, preferably a basic catalyst, the basic catalyst is preferably selected from the group of alkali metal hydroxides, more preferably comprises at least KOH.

In a preferred embodiment of the process for preparing monomers of the general formula (II) and / or oligomers of the general formula (III) as described above, step ii) takes place at a pressure in the range from 0 to 500 bar, preferably 0.1 to 200 bar, more preferably 0.5 to 100 bar, more preferably 1 to 20 bar. Step ii) is preferably carried out in a, preferably closed, system, more preferably in an autoclave. Step ii) is preferably carried out for a period of time in the range from 10 seconds to 7 days, preferably 5 minutes to 24 hours, preferably from 30 minutes to 2 hours.

In a preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) as described above, after ii) and before iii) the alcoholic and / or aqueous mixture obtained according to ii) comprising monomers is carried out of the general formula (II) cooled, preferably to a temperature in the range from -100 to + 200 ° C, preferably -60 to +60 ° C, more preferably -30 to +30 ° C, and / or the pressure to a value is reduced in the range from 0.8 to 1.2 bar.

The separation of the monomers of the general formula (II) and / or oligomers of the general formula (III) according to iii) is preferably carried out by means of one or more processes from the group consisting of precipitation, preferably by means of precipitation reagents, filtration, crystallization, centrifugation, distillation, evaporation and chromatography.

In a preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) as described above, the polyethylene-like polymer has a repeating unit of the general formula (Ia)

[X ¹ - (CH ₂ ) a-] n

(la) on, where

X ^{1 is} selected from C (= 0) -0- group and -0-C (= 0) -group; a is an integer from 8 to 200. Polyethylene-like polymers which have a repeating unit of the general formula (Ia) are also referred to as “polyesters”. The index “a” can be the same or different for each of the n repeating units of the general formula (Ia), ie with n repeating units there is a maximum of n different values for the index “a”. “X ¹ ” can be the same or different for each of the n repeating units, ie each of the n X ¹ groups is independently selected from C (= 0) -0-group and -0-C (= 0) -group. The index “n”, which is given for the repeating unit of the general formula (Ia), stands for an integer from the range from 8 to 60,000, more preferably from the range from 2 to 58,562 - this corresponds to an M _n in the range from 5,000 to 10,000,000 g / mol a percentage of 90 - 99.5 mol% methylene groups in the polymer. More preferably, n in (Ia) is an integer from the range from 4 to 60,000, more preferably from the range from 4 to 58,562 - this corresponds to _{a percentage of 90 for an M n} in the range from 10,000 to 10,000,000 g / mol - 99.5 mol% methylene groups in the polymer. More preferably, n in (Ia) stands for an integer from the range from 8 to 60,000, more preferably from the range from 8 to 58,562 - this corresponds to _{a percentage of with an M n} in the range from 20,000 to 10,000,000 g / mol 90-99.5 mol% methylene groups in the polymer, corresponding to 8-200 methylene groups per functional group in (la). In a further preferred embodiment, n in (Ia) stands for an integer from the range from 18 to 60,000, more preferably from the range from 18 to 58,562 - this corresponds to an M _n in the range from 50,000 to 10,000,000 g / mol a percentage of 90-99.5 mol% methylene groups in the polymer.

In (Ia), n is preferably an integer from the range from 8 to 47,000, more preferably from the range from 8 to 46,984 - this corresponds to _{a percentage of 92 for an M n} in the range from 5,000 to 10,000,000 g / mol - 98 mol% of methylene groups in the polymer. More preferably, n in (Ia) stands for an integer from the range from 14 to 47,000, more preferably from the range from 14 to 46,984 - with an M _n in the range from 10,000 to 10,000,000 g / mol this corresponds to a percentage of 92 - 98 mol% methylene groups in the polymer. In a further preferred embodiment, n in (Ia) stands for an integer from the range from 28 to 47,000, more preferably from the range from 28 to 46,984 - this corresponds to an M _n in the range from 20,000 to 10,000,000 g / mol a percentage of 92-98 mol% methylene groups in the polymer, corresponding to 12-49 methylene groups per functional group in (la). In a further preferred embodiment, n in (Ia) stands for an integer from the range from 70 to 47,000, more preferably from the range from 70 to 46,984 - this corresponds to an M _n in the range from 50,000 to 10,000,000 g / mol a percentage of 92-98 mol% methylene groups in the polymer.

In a particularly preferred embodiment of the process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) as described above, the polyethylene-like polymer has a repeating unit of the general formula (Ib)

[-0-C (= 0) -0- _(CH2) a-] n (lb), where a is an integer from 8 to 200.

Polyethylene-like polymers which have a repeating unit of the general formula (Ib) are also referred to as “polycarbonates”. The index “a” can be the same or different for each of the n repeating units of the general formula (lb), ie with n repeating units there is a maximum of n different values for the index “a”. The index “n”, which is given for the repeating unit of the general formula (lb), stands for an integer from the range from 2 to 60,000, more preferably from the range from 2 to 56,000, more preferably from the range from 2 to 53,546 - with an M _n in the range from 5,000 to 10,000,000 g / mol, this corresponds to a percentage of 90-99.5 mol% methylene groups in the polymer. More preferably, n in (lb) stands for an integer from the range from 4 to 60,000, more preferably from the range from 4 to 53,546 - with an M _n in the range from 10,000 to 10,000,000 g / mol this corresponds to a percentage of 90 - 99.5 mol% methylene groups in the polymer. More preferably, n in (lb) stands for an integer from the range from 8 to 60,000, more preferably from the range from 8 to 53,546 - with an M _n in the range from 20,000 to 10,000,000 g / mol this corresponds to a percentage of 90 - 99.5 mol% methylene groups in the polymer, corresponding - 200 methylene groups per functional group in (lb). More preferably, n in (lb) stands for an integer from the range from 18 to 60,000, more preferably from the range from 18 to 53,546 - with an M _n in the range from 50,000 to 10,000,000 g / mol this corresponds to a percentage of 90 - 99.5 mol% methylene groups in the polymer.

In (lb), n is preferably an integer from the range from 8 to 47,000, more preferably from the range from 8 to 43,698 - this corresponds to _{a percentage of 92 for an M n} in the range from 5,000 to 10,000,000 g / mol - 98 mol% of methylene groups in the polymer. More preferably, n in (lb) stands for an integer from the range from 14 to 47,000, more preferably from the range from 14 to 43,698 - with an M _n in the range from 10,000 to 10,000,000 g / mol this corresponds to a percentage of 92 - 98 mol% methylene groups in the polymer. More preferably, n in (lb) stands for an integer from the range from 28 to 47,000, more preferably from the range from 28 to 43,698 - with an M _n in the range from 20,000 to 10,000,000 g / mol this corresponds to a percentage of 92-98 mol% methylene groups in the polymer, corresponding to 12-49 methylene groups per functional group in (lb). More preferably, n in (lb) stands for an integer from the range from 68 to 47,000, more preferably from the range from 68 to 43,698 - this corresponds to _{a percentage of 92 for an M n} in the range from 50,000 to 10,000,000 g / mol - 98 mol% of methylene groups in the polymer.

The alcoholic and / or aqueous mixture obtained in ii) preferably comprises monomers of the general formula (II) and / or oligomers of the general formula (III) furthermore monomers of the general formula (IV)

R ¹ -0-C (= 0) -0-R ²

(iv) , whereby

R ¹ , R ^{2 are} each a C1-C10-alkyl group, preferably a C1-C5-alkyl group, more preferably a C1- or C2-alkyl group; where the monomers of the general formula (IV) are preferably separated off in iii) together with the monomers of the general formula (II) and / or oligomers of the general formula (III) from the alcoholic and / or aqueous mixture obtained according to ii).

The monomers of the general formula (II) and / or the oligomers of the general formula (III) in a yield of> 90 mol%, preferably> 92 mol%, more preferably> 94 mol%, are more preferred of> 96 mol%, based on the polyethylene-like polymer used.

3rd aspect - composition

A third aspect of the invention relates to a composition comprising a monomer of the general formula (II) and / or an oligomer of the general formula (III)

Y ¹ - (CH ₂ ) _C -Y ²

(II) where Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) group or -C (= 0) -0-R group and OFI group, where R is a hydrogen atom or a C1-C10-alkyl group, preferably a hydrogen atom or a C1-C5-alkyl group, more preferably a hydrogen atom or a C1- or C2-alkyl group; and the index c is an integer from the range 8 to 200,

Y ¹ - [(CH ₂ ) _a -X-] mY ²

(III)

, whereby

Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) -0-group or -O- C (= 0) -0-R-group, R-0-C (= 0) -Group or -C (= 0) -0-R group and OFI group, where R is a hydrogen atom or a C1-C10-alkyl group, preferably a hydrogen atom or a C1-C5-alkyl group, more preferably a hydrogen atom or a C1- or C2-alkyl group; X is selected from the C (= 0) -0 group or -0-C (= 0) group and-0-C (= 0) -0 group, where X is in the last repeating unit of formula (III) , ie when transitioning to Y ² , does not exist; a is an integer from the range 8 to 200; and the subscript m is an integer from the range 2 to 40; obtained or obtainable by the process of the 2nd aspect. As already described in the 2nd aspect, the index “a” can be the same or different for each of the n repeating units of the general formula (III), ie with m repeating units there is a maximum of n different values for the index "a". Likewise, “X” can be the same or different for each of the m repeating units, ie each of the n X groups is independently selected from C (= 0) -O-group or -0-C (= 0) -group and -0 -C (= 0) -0- group. X is not present in the last repeating unit in the oligomers of the general formula (III). This means, for example for m = 2, the following structure of an oligomer of the general formula (III):

Y ¹ - [(CH ₂ ) aX -] - [(CH ₂ ) a -] - Y ²

The structure for oligomers of the general formula (III) with m in the range from 3 to 40 is analogous. The composition preferably further comprises a monomer of the general formula (IV) R ¹ -0-C (= 0) -0-R ²

(iv)

, where R ¹ , R ^{2 are} each a C1-C10-alkyl group, preferably a C1-C5-alkyl group, more preferably a C1- or C2-alkyl group.

4th aspect - use for re-polymerization

According to a fourth aspect, the invention relates to the use of the composition of the third aspect for the production of polymers, in particular polyethylene-like polymers comprising methylene groups and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group, preferably 90 to 99.5 mol%, more preferably 92 to 98 mol%, of the polyethylene-like polymer consisting of methylene units (CH2).

With regard to the use, the polyethylene-like polymer preferably has a repeating unit of the general formula (I)

[-X- (CH ₂ ) _a -j

(I) on, where

X is selected from C (= 0) -0- group or -0-C (= 0) -group and-0-C (= 0) -0- group; a is an integer from 8 to 200. In a preferred embodiment, the general formula (I) is as follows: [-X- (CH ₂ ) _a -] _n , where X ”and“ a ”have the meaning given. As already described in the 2nd aspect, the index “a” can be the same or different for each of the n repeating units of the general formula (III), ie with n repeating units there is a maximum of n different values for the index “a”. Likewise, “X” can be the same or different for each of the n repeating units, ie each of the n X groups is independently selected from C (= 0) -0-group or -0-C (= 0) -group and -0 -C (= 0) - O- group. The preferably polyethylene-like polymer used has a number average molecular weight (M _n ) in the range from 5,000 to 10,000,000 g / mol, preferably in the range from 10,000 to 10,000,000 g / mol. In preferred embodiments, it has a number average molecular weight (M _n ) in the range from 20,000 to 10,000,000 g / mol or in the range from 50,000 to 10,000,000 g / mol. _{M n} is determined by means of gel permeation chromatography (GPC) against polystyrene standards in the range of 400-5,000,000 g / mol (universal calibration). Details regarding the, preferably polyethylene-like, polymer are as described above for the second aspect of the invention; accordingly, reference is made here to all the details relating to the polymer described in relation to the second aspect of the invention.

5th aspect - method for producing a prefabricated part by means of primary molding

According to a fifth aspect, the invention relates to a method for producing a finished part. The finished part can be a component of a device, such as, for example, a component of a machine. For example, the finished part is a gear. The method includes providing a material comprising a polyethylene-like polymer. The polyethylene-like polymer comprises methylene groups (CH2) and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group. Details relating to the, preferably polyethylene-like, polymer are as described above for the second aspect of the invention. Correspondingly, reference is made here to all the details relating to the polymer described in relation to the second aspect of the invention. The prefabricated part is produced by molding the material provided in this way.

In the context of the present invention, “archetypes” can in particular be understood to mean a production method according to DIN 8580, in which a solid body is produced from a shapeless material, which has a geometrically defined shape. Archetypes are used to produce the initial form of a solid body and to create the cohesion of the material. In principle, starting materials in liquid, gaseous, plastic, granular or powdery state can be used for the primary shaping, i.e. with different rheological behavior.

In particular, the primary shaping of the material includes thermal primary shaping, i.e. primary shaping with simultaneous supply of heat. In principle, in the context of the present invention, the primary molding is at least one method selected from the group consisting of: injection molding, extrusion, calendering, rotational molding, injection blow molding.

It is explicitly emphasized that this method can be used to produce any finished part that can be produced by means of primary molding of the material described.

6th aspect - method for manufacturing a finished part by means of additive manufacturing

According to a sixth aspect, the invention relates to a method for producing a finished part from a material, the material comprising a polyethylene-like polymer. The polyethylene-like polymer comprises methylene groups (CH2) and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group. Details relating to the, preferably polyethylene-like, polymer are as described above for the second aspect of the invention. Correspondingly, reference is made here to all the details relating to the polymer described in relation to the second aspect of the invention. The finished part is manufactured using an additive manufacturing process.

In the context of the present invention, an “additive manufacturing process” can in particular be understood to mean a manufacturing process in which the material is applied layer by layer and thus three-dimensional objects (workpieces) are produced. The layer-by-layer structure is computer-controlled from one or more liquid or solid materials according to specified dimensions and shapes. When building, find physical or chemical hardening or melting processes take place. Although it is often a molding process, no special tools such as casting molds are required for a specific product, which have stored the respective geometry of the workpiece. The additive manufacturing process is preferably 3-D printing.

In the context of the present invention, “3-D printing” can be understood to mean, in particular, a manufacturing method in which the material is applied layer by layer and three-dimensional objects (workpieces) are produced in this way. The layer-by-layer structure is computer-controlled from one or more liquid or solid materials according to specified dimensions and shapes. Physical or chemical hardening or melting processes take place during construction. Although it is often a molding process, no special tools such as casting molds are required for a specific product, which have saved the respective geometry of the workpiece. In principle, it can be a process in accordance with the current draft standard DIN EN ISO / ASTM 52900: 2018 and thus free-jet binder application, material application with directed energy input, material extrusion, free-jet material application, powder bed-based melting, layer lamination or bath-based photopolymerization.

In the process, the material is provided as a filament.

In the context of the present invention, “filament” can be understood to mean in particular thermoplastic plastics made from the material described above, which are used in wire form, especially made up on rolls, in the FDM / FFF process (FDM - Fused Deposition Modeling; FFF - Fused Filament Fabrication) .

EXAMPLES

The invention is illustrated below with the aid of examples, without being restricted to these.

Example 1 - Synthesis of Polycarbonate-18

In a typical polycondensation reaction for the production of PC-18, a three-neck Schlenk tube filled with 1, 18-octadecanediol (1 equiv.) And a magnetic stirrer was closed with a silicone septum and dried under vacuum for at least 1 hour at 60 ° C. After flushing the structure with nitrogen, a condensation bridge with round bottom flask and bubble counter was attached to the Schlenk tube. Diethyl carbonate (2.5 equiv.) Was added in a nitrogen countercurrent and the reaction mixture was heated to 120 ° C. (stirring at 500 rpm) until a homogeneous mixture had formed. In the next step, a suspension of LiFH (0.7 mol%) in diethyl carbonate was added. After about 15-45 minutes, the ethanol began to condense out over the condensation bridge. The reaction conditions were maintained until condensate no longer formed. In the next step, the bubble counter on the condensation bridge was replaced by a membrane pump and the The oligomerization reaction was continued at 180 ° C. under reduced pressure (900 mbar to 10 mbar). Following the oligomerization, the structure was flushed with nitrogen, the condensation bridge was replaced by a glass stopper and a high vacuum (~ 1-5 x 10 ² mbar) was applied via the Schlenk line. The magnetic stirrer was switched off due to the high viscosity of the polymer melt already reached at this point in the reaction. The polycondensation reaction was continued until the polymer melt was no longer flowable due to the high viscosity. In order to bring the resulting polymer into solution, xylene was added in a nitrogen countercurrent at 120 ° C. in the next step. After the polymer melt had been loosened with a spatula, the magnetic stirrer was switched on again. After about 30-60 minutes, a homogeneous solution of the polymer had formed, which was precipitated in cold propan-2-ol. The precipitated solid was washed repeatedly in propan-2-ol and finally dried overnight in a vacuum drying cabinet. The yield was typically over 95 mol% PC-18 based on the 1,18-octadecanediol used. The polymer was characterized by ¹ H and ¹³ C-NMR spectroscopy, IR spectroscopy, gel permeation chromatography and a tensile strain experiment. The mechanical properties of the polymer were in the typical range of polyethylene-like materials with an elongation at break of 200-400% with a modulus of elasticity of 500 to 1000 MPa. The polymer had a number average molecular weight (M _n ) of 88 kg / mol.

Example 2 - Synthesis of Polycarbonate-48

PC-48 was synthesized from 1,48-octadecanediol analogously to the described production of PC-18 according to Example 1, 1,48-octadecanediol being produced from erucic acid by means of a catalytic process published elsewhere. 1,48-octadecanediol (10.0 g) were dried in a three-necked Schlenk tube with a magnetic stirrer at 100 ° C and then with diethyl carbonate (8.5 ml, 5 equiv.) And LiH (1.1 mg, 1 mol%) offset. The reaction mixture was oligomerized analogously to the synthesis of PC-18 and then polymerized at 180 ° C. for 72 h in order to achieve a viscosity comparable to the melt of PC-18. The resulting polymer was finally dissolved in xylene in portions and precipitated in cold propan-2-ol. The precipitated solid could be obtained in quantitative yield by filtration (10.19 g, 98%). The polymer was characterized by ¹ H and ¹³ C-NMR spectroscopy, IR spectroscopy and gel permeation chromatography. The polymer had a number average molecular weight (M _n ) of 40 kg / mol.

Example 3 - Synthesis of Polyester-18.18

In a typical polycondensation reaction for the production of PE-18,18, a three-necked Schlenk tube filled with 1, 18-octadecanediol (1 equiv.), 1, 18-dimethyloctadecanedioate (1 equiv.) And a magnetic stirrer was closed with a silicone septum and dried for at least 1 hour at 60 ° C under vacuum. After flushing the structure with nitrogen, a condensation bridge with round bottom flask and bubble counter was attached to the Schlenk tube. In the next step, titanium (IV) butoxide (0.084 mol%) was added to the reaction mixture in a nitrogen countercurrent and the temperature was increased to 180 ° C. (stirring at 350 rpm). After about 15-45 minutes, methanol began to condense out over the Condensation bridge. The reaction conditions were maintained until condensate no longer formed. In the next step, the bubble counter on the condensation bridge was replaced by a membrane pump and the oligomerization reaction was continued at 180 ° C. under negative pressure (900 mbar to 10 mbar). Following the oligomerization, the condensation bridge was replaced by a glass stopper and a high vacuum (~ 1-5 x 10 ² mbar) was applied via the Schlenk line. Due to the high viscosity of the polymer melt already reached at this point in time of the reaction, the magnetic stirrer was switched off. The polycondensation reaction was continued until the polymer melt was no longer flowable due to the high viscosity. In order to bring the resulting polymer into solution, xylene was added in a nitrogen countercurrent at 160 ° C. in the next step. After the polymer melt had been loosened with a spatula, the magnetic stirrer was switched on again. After about 30-60 minutes, a homogeneous solution of the polymer had formed, which was precipitated in cold propan-2-ol. The precipitated solid was washed repeatedly in acetone and finally dried overnight in a vacuum drying cabinet. The yield was typically over 95 mol% of PE-18.18 based on the amount of monomer used. The polymer was characterized by ¹ H and ¹³ C-NMR spectroscopy, IR spectroscopy and gel permeation chromatography. The mechanical properties of the polycondensate were in the typical range of polyethylene-like materials with an elongation at break of 350-500% and a modulus of elasticity of 900 to 1100 MPa. The polymer had a number average molecular weight (M _n ) of 50 kg / mol.

Example 4 - Extrusion of 3D Printing Filament: Experimental Setup and Procedure

For the production of 3D printing filament on a laboratory scale, a nozzle was used which was connected to a laboratory compounder Xplore MC-5 and thus allowed the extrusion of dimensionally accurate filament of the polycondensates described. The polymer melt emerging from the compounder was passed through the nozzle, cooled down in the process and emerged from the nozzle as a dimensionally stable filament. Typically, the nozzle attached to the compounder was first preheated to the temperature of the compounder for about 5 minutes. The filament was then extruded with the respective material-specific parameters. A single compounder filling allowed approx. 4 g of filament to be extruded. In semi-continuous operation (ie the compounder was refilled while filament extrusion was paused), up to 23 g of filament could be extruded in one piece, only limited by the amount of polymer present. Example 5 - Extrusion of 3D printing filament: process parameters

Two commercially available dyes (Omnidynamics MBR and MBB) and carbon fiber (diameter ~ 7 mm ± 2, length: 200 mm ± 30) were selected as examples for typical polymer additives in order to produce the corresponding compounds with PC-18 and PE-18,18 . To produce dyed filaments, 4.85 g of PC-18 or PE-18.18 were compounded with 150 mg (3% by weight) of dye at 150 ° C. for at least 30 minutes and then extruded as a filament. To produce carbon fiber-reinforced PC-18, 4.5 g of polymer were compounded with 500 mg of carbon fiber at 170 ° C. for 30 minutes and then extruded as a filament. To produce black PC-48, 5 g of polymer were compounded with 100 mg of carbon fiber at 170 ° C. for 30 minutes and then extruded as a filament. The diameters of the filaments produced with the described process ranged from 1.66 - 1.81 mm with a standard deviation of 0.01 - 0.02 mm (see diameter of commercial filament: 1.75 ± 0.05 mm) .

Example 6a - Depolymerization of PC-18

For the depolymerization of larger amounts of PC-18, a steel autoclave with a glass insert was used (300 ml usable internal volume). For this purpose, 20.0 g (64 mmol) PC-18 (melt-processed, coarsely comminuted pieces), 250 ml KOH basic EtOH (10% by weight with respect to PC-18) and a magnetic stir bar were placed in the glass insert. The autoclave was heated to 120 ° C. on a hot plate and magnetically stirred at 500 revolutions per minute. After the typical depolymerization time of 1 to 24 hours, the heater was switched off and the autoclave was cooled to 40 ° C. The warm solution was quantitatively rinsed into a beaker with EtOH. The mixture was evaporated and then recrystallized from MeOH. The temperature of the mixture during the filtration was -30 ° C. in order to ensure quantitative separation. The filtered solids were dried and 17.91 g, corresponding to 98 mol% (based on PC-18 used), of 1,18-octadecanediol were recovered. The purity of> 99% was determined by gas chromatography (FID).

Example 6b - Hydrolysis of PC-18

A steel autoclave with a glass insert was used for the hydrolysis of PC-18. For this purpose, 200 mg PC-18 (melt-processed, coarsely comminuted pieces), 5 ml KOH basic water (50% by weight with respect to PC-18) and a magnetic stir bar were placed in the glass insert. The autoclave was heated to 180 ° C. on a hot plate and stirred at 500 revolutions per minute. After a depolymerization time of 24 hours, the heater was switched off and the autoclave was cooled to room temperature. The solids were filtered off, washed with water and dried. The yield of 1,18-octadecanediol was> 98% and the product was characterized by means of ¹ H-NMR, the ¹ H-NMR spectrum being shown in FIG.

Example 7 - Separation of PC-18 from polyolefins by depolymerization In order to simulate the separation of PC-18 from a typical plastic waste mixture of polyolefins, as they occur in industrial waste sorting, a blue-colored piece of a 3D-printed PC-18 piece was mixed with one colored piece of commercial polypropylene as well as polyethylene together in a glass insert for pressure reactors with KOH basic MeOH (10% by weight with respect to PC-18) depolymerized (100 ° C., 500 revolutions per minute for 24 h to ensure complete conversion). The completeness of the reaction was ^{demonstrated by 1} H-NMR spectroscopy. The two remaining pieces of polyolefin were washed with MeOH and dried after the experiment. The two polyolefins showed no weight loss, and the color of the plastics themselves was unchanged, but there were blue spots on the surface due to the deposited dye of the colored PC-18. The filtrates from the reaction were combined and evaporated to dryness. After recrystallization from MeOH, the colorless monomer 1,18-octadecanediol was recovered almost quantitatively to 180.1 mg, corresponding to 98 mol% (based on the PC-18 used). The purity of> 99% was determined with gas chromatography (FID).

Example 8 - Depolymerization of PE-18.18

In order to be able to follow the progress of the reaction, the depolymerization of PE-18.18 (25.0 g of uncolored polymer or 5.0 g of polymer colored by means of Omnidynamics MBR) was carried out in a glass tube autoclave (500 ml volume). In a typical depolymerization experiment, the glass tube was filled with a strong lanthanoid magnetic stir bar, melt-processed and pre-cut PE-18.18 and methanol (16 ml per 1 g PE-18.18) and heated in a heating block (120 ° C at 200 U / min).

After a typical depolymerization time of 2 to 24 hours, the reaction mixture was transferred quantitatively to a round bottom flask and the methanol solvent was then removed under reduced pressure.

This method provided a colorless, stoichiometrically exact 1: 1 mixture of the two monomers used (1,18-octadecanediol and 1,18-dimethyloctadecanedioate), which ^{could be demonstrated by 1} H-N MR experiments. The yield was quantitative (27.6 g of the 1: 1 monomer mixture of 25.0 g of PE-18.18).

Successful, analogous depolymerization experiments with PE-18,18 were carried out on a small scale (200 mg polymer) also at higher temperatures (eg 150 ° C.) and with a catalyst (eg 10% by weight KOH) in metal autoclaves. Example 9 - Repolymerization to PE-18.18

The 1: 1 monomer mixture from example 8 could without purification analogously to the described production of “virgin” PE-18,18 from example 3 to give equivalent polymer (ie no deterioration in the mechanical and chemical properties of the material, such as due to tensile strain, among others Experiments, ¹ H-NMR and gel permeation chromatography could be shown) to be repolymerized. The polymer had a number average molecular weight (M _n ) of 79 kg / mol.

Example 10 - Depolymerization of PE-18.18 with Impurities

To simulate contamination, black-colored polypropylene - as an example of a widely used commercial plastic - was added to the PE-18, 18 and depolymerization was carried out as in Example 8. The black-colored polypropylene was unchanged after the process and could easily be removed from the colorless monomer mixture using tweezers.

In the case of the depolymerization of PE-18,18 dyed using Omnidynamics MBR, the reaction mixture was transferred to a round-bottomed flask after the depolymerization, whereby the dye used remained in the glass tube autoclave (sticking as a whole piece to the bottom of the reactor and theoretically reusable) and thus effective and simple could be separated. The complete separation of the dye could be ^{demonstrated by 1} H-NMR experiments. These showed that a repolymerizable, stoichiometrically exact 1: 1 mixture of the two monomers used was again obtained.

Example 11 - 3D printing using extruded filament

A commercially available, unmodified printer of the Prusa brand with the model name Prusa i3 MK3 was used for the 3D printing of the polycondensates described. This was equipped with a pressure bed made of stainless steel, covered with a polyetherimide film (PEI).

11.1 Tensile strain test specimen according to ISO 527-2, type 5A

Tensile strain test specimens according to ISO 527-2-5A were produced from all the polymers described with the following settings:

Nozzle diameter: 0.8 mm

Nozzle temperature: 230 ° C

Bed temp .: 100 ° C

Printing speed: 5 mm / s

Layer height: 0.4 mm, general extrusion width: 0.8 mm

Fan cooling: completely deactivated FIG. 1 shows a stress-strain diagram for tensile-strain test pieces 100, 102, 104, 106 according to ISO 527-2-5A made from PC-18, which were produced by means of the printer with the specified parameters. The PC-18 filaments mentioned in Example 4 and Table 1 were used as starting materials for the measurement results shown by way of example in FIG. The elongation is indicated in% on the X-axis 108. The stress is indicated in MPa on the Y-axis 110. For the sake of clarity, the curves only represent the result of a measurement according to ISO 527-2-5A, which are within the fluctuation of all test specimens examined. In FIG. 1, curve 112 indicates the measurement result for a white test body 100, curve 114 indicates the measurement result for a red test body 102, curve 116 indicates the measurement result for a blue test body 104 and curve 118 indicates the measurement result of a carbon fiber-reinforced one Blends as material for the test body 106 for comparison.

The mechanical properties of the tensile-strain test specimens 100, 102, 104, 106 (ISO 527-2-5A) produced from PE-18, 18 and PC-18 using 3D printing correspond to the polyethylene-like properties of those using injection molding from the same polymers manufactured test specimen. With the polymers described in this patent, HDPE-like properties can thus be achieved using both injection molding and 3D printing.

11.2 Protective cover for smartphone (suitable for iPhone 11 Pro) made of PE-18,18 The printing parameters for producing a protective cover 200 for a smartphone made of PE-18,18 are given below. It is an excerpt of the relevant parameters from the G-code used to manufacture the object:

; external perimeters extrusion width = 0.45mm; perimeters extrusion width = 0.45mm; infill extrusion width = 0.45mm; solid infill extrusion width = 0.45mm; top infill extrusion width = 0.40mm; first layer extrusion width = 0.42mm

M201 X1000 Y1000 Z1000 E5000; sets maximum accelerations, mm / sec ^A 2 M203 X200 Y200 Z12 E120; sets maximum feedrates, mm / sec

M204 P1250 R1250 T1250; sets acceleration (P, T) and retract acceleration (R), mm / sec ^A 2

M205 X8.00 Y8.00 Z0.40 E1 .50; sets the jerk limits, mm / sec

M104 S200; set extruder temp

M140 S95; set bed temp

M 190 S95; wait for bed temp

M 109 S200; wait for extruder temp

; estimated printing time (normal mode) = 1h 0m 37s

; avoid_crossing_perimeters = 1 bed_shape = 0x0,250x0,250x210,0x210 bed_temperature = 95 bridge_acceleration = 1000 bridge_fan_speed = 50 brim_width = 10 colorprint_heights = complete_objects = 0 cooling = 0 cooling_tubeJength = 5 cooling_tube_retraction = 91.5 default_acceleration = 1000 deretract_fan_speeding = 6 default_acceleration = 1000 deretract_loading_speed = 0 disable_firstdistance = 91.5 default_acceleration = 1000 duplicate_fan_loading = 6 extra_acceleration = 4 disable_firove_loading_first = 6 2 extruder_clearance_height = 20 extruder_clearance_radius = 20 extruder_colour = # FFFF00 extruder_offset = 0x0 extrusion_axis = e extrusion_multiplier = 0.97 fan_always_on = 0 fan_below_layer_time = 100 filament_colour = # DEE0E6 filament_cooling_final_speed = 3.4 filament_cooling_initial_speed = 2.2 filament_cooling_moves = 4 filament_cost = 72 filament_density = 0.89 filament_diameter = 1.6 filamentJoad_time = 0 filament_loading_speed = 28 filament_loading_speed_start = 3 filament_max_volumetric_speed = 5 filament_minimal_purge_on_wipe_tower = 15 filament_soluble = 0 filament_toolchange_delay = 0 filament_type = PP filament_unload_time = 0 filament_unloading_speed = 90 filament_unloading_speed_start = 100 first_layer_acceleration = 1000 first_layer_bed_temperature = 95 first_layer_extrusion_width = 12:42 first_layer_speed first_layer_temperature = 30 = 200 = 0 gcode_comments gcode_flavor = marlin gcodeJabel_objects = 0 = 0 high_current_on_filament_swap infill_acceleration = 1250 = 0 infilLfirst machine_max_acceleration_e = 5000.5000 machine_max_acceleration_extruding = 1250.1250 1250.1250 machine_max_acceleration_retracting = machine_max_acceleration_x = 1000.960 machine_max_acceleration_y = 1000 .960 machine_max_acceleration_z = 1000.1000 machine_max_feedrate_e = 120.120 machine_max_feedrate_x = 200.100 machine_max_feedrate_y = 200.100 machine_max_feedrate_z = 12.12 machine_max_jerk_e = 1.5,1.5 machine_max_jerk_e = 1.5,1.5 machine_max_jerk_e = 1.5,1.5 machine_max_max_jerk_x = 0, 8 machine_max_jerk_jerk_rate = 0.4, machine_max_jerk_jerk_x = 0, 8 machine_max_jerk_jerk_x = 0.4 machine_max_jerk_jerk_x = 0.4 0 max_fan_speed = 30 max_layer_height = 0.25 max_print_height = 210 max_print_speed = 200 max_volumetric_speed = 0 min_fan_speed = 30 min_layer_height = 0.07 min_print_speed = 15 min_skirt_length = 4 notes = nozzle_diamete r = 0.4 only_retract_when_crossing_perimeters = 0 ooze_prevention = 0 parking_pos_retraction = 92 perimeter_acceleration = 800 post_process = printer_model = MK3 resolution = 0 retract_before_travel retract_before_wipe = 1 = 0% retract_layer_change = 1 retractjength = 1 retract_length_toolchange = 4 retractjift = 0.4 retract_lift_above = 0 retract_lift_below = 209 retract_restart_extra = 0 retract_restart_extra_toolchange = 0 retract_speed = 20 silent_mode = 1 single_extruder_multi_material = 0 single_extruder_multLmaterial_priming = 0 skirt_distance = 2 skirt_height = 1 skirts = 0 slowdown_below_layer_time = 20 spiral_vase = 0 = -5 standby_temperature_delta temperature = 200 threads = 4 toolchange_gcode = travel_speed = 180 use_firmware_retraction = 0 = 1 use_relative_e_distances use_volumetric_e = 0 variable_layer_height = 1 = 0 wipe wipe_tower wipe_tower_bridging = 1 = 10 = 0 wipe_tower_rotation_angle wipe_tower_width = 60 wipe_tower_x = 170 wipe_tower_y = 125 wiping_volumes_extruders = 70.70 wiping_volumes_matrix = 0 z_offset = 0 clip_multipart_objects = 1 dont_support_bridges = 1 elefant_foot_compensation = 0 extrusion_width = 0.45 first_layer_he .2 infill_only_where_needed = 0 interface_shells = 0 layer_height = 0.2 raftjayers = 0 seam_position = nearest slice_closing_radius = 0.049 support_material = 0 support_material_angle = 0 support_material_auto = 1 support_material_buildplate_only = 0 support_material_contact_distance = 0.1 support_material_enforce_layers = 0 support_material_extruder = 0 support_material_extrusion_width = 00:35 support_materialJnterface_contact_loops = 0 support_material_interface_extruder = 0 support_material_interfaceJayers = 2 support_material_interface_spacing = 0.2 support_material_interface_speed = 100% support_material_pattern = rectilinear support_material_spacing = 2 support_material_speed = 40 support_material_synchronize_layers = 0 support_material_threshold = 55 support_material_with_sheath = 0 support_material_xy_spacing = 50% wipe_into_objects = 0 xy_size_compensation = 0 bottom_fill_pattern = rectilinear bottom_solid_layers = 4 bridge_angle = 0 bridge_flow_ratio = 0.95 bridge_speed = 40 ensu re_vertical_shell_thickness = 1 external_perimeter_extrusion_width = 0.45 external_perimeter_speed = 40 external_perimeters_first = 0 extra_perimeters = 0 filLangle = 45 filLdensity = 100% filLpattern = rectilinear gap_fill_speed = 40 infill_every_layers = 1 ; infilLextruder = 1; infill_extrusion_width = 0.45; infilLoverlap = 50%

; infilLspeed = 40; overhangs = 0; perimeter_extruder = 1; perimeter_extrusion_width = 0.45; perimeter_speed = 40; perimeters = 2; small_perimeter_speed = 40; solid_infill_below_area = 0; solidJnfilLeveryJayers = 0; solidJnfilLextruder = 1; solid_infill_extrusion_width = 0.45; solidJnfilLspeed = 40; thin_walls = 0; to p_f i I Lpatte rn = rectilinear; top_infill_extrusion_width = 0.4; top_solid_infill_speed = 40; top_solid_layers = 5; wipejntojnfill = 0; print_settings_id = 0.20mm PE-18.18; filament_settings_id = PE-18.18; printer_settings_id = Original Prusa i3 MK3 PE-18,18; printer_model = MK3; printer_variant = 0.4

Figure 2A shows the front view and Figure 2B the corresponding rear view of the smartphone protective cover 200 made of PE-18,18. As can be seen from Figures 2A and 2B, very good printability can be achieved with the material PE-18,18, which enables (additive) manufacturing even of complex objects.

11.3 Colored espresso cup made from PC-48

The printing parameters for making a small cup 300 made from colored PC-48 are given below. It is an extract of the relevant parameters from the G code used to create the object:

; external perimeters extrusion width = 0.45mm; perimeters extrusion width = 0.45mm; infill extrusion width = 0.45mm; solid infill extrusion width = 0.45mm; top infill extrusion width = 0.40mm ; first layer extrusion width = 0.42mm

M204 P1250 R1250 T1250; sets acceleration (P, T) and retract acceleration (R), mm / sec ^A 2 M205 X8.00 Y8.00 Z0.40 E1 .50; sets the jerk limits, mm / sec M205 SO TO; sets the minimum extruding and travel feed rate, mm / sec M104 S250; set extruder temp M140 S100; set bed temp M190 S100; wait for bed temp M 109 S250; wait for extruder temp estimated printing time (normal mode) = 1h 48m 3s avoid_crossing_perimeters = 0 bed_shape = 0x0,250x0,250x210,0x210 bed_temperature = 100 between_objects_gcode = bridge_acceleration = 1000 bridge_fan_speed = 0 brim_width = 0 colorprint_heights = complete_object = 0 cooling_print_heights = complete_object = 0 cooling = 5 cooling_tube_retraction = 91.5 default_acceleration = 1000 deretract_speed = 0 disable_fan_first_layers = 3 duplicate_distance = 6 end_filament_gcode = Filament-specific end gcode "extra_loading_move = -2 extruder_clearance_height = 20 extruder_clearance_height = 20 extruder_clearance_height = 20 extruder_clearance_radius = 0x extrusion_fourways_Fourways = 20 extrusion_offuder_Foural = 0x extrusion_fourways_four = 0x extrusion_off 1 fan_below_layer_time = 10 filament_colour = # FF8000 filament_cooling_final_speed = 3.4 filament_cooling_initial_speed = 2.2 filament_cooling_moves = 4 filament_cost = 21.2 filament_density = 1.2 filament_diameter filament_loading_speed = 1 .65 filament_load_time = 0 = 28 = 3 filament_loading_speed_start filament_max_volumetric_speed = 8 filament_minimal_purge_on_wipe_tower = 15 filament_notes = "" filament_soluble = 0 = 0 filament_toolchange_delay filament_type = PLA filament_unload_time = 0 filament_unloading_speed filament_unloading_speed_start = 90 = 100 = 1000 first_layer_acceleration first_layer_bed_temperature = 100 first_layer_extrusion_width = 12:42 = 5 first_layer_speed firstjayer_temperature = 250 gcode_comments = 0 gcode_flavor = marlin gcode_label_objects = 0 = 0 high_current_on_filament_swap infill_acceleration = 1250 = 0 infilLfirst machine_max_acceleration_e = 5000.5000 machine_max_acceleration_extruding = 1250.1250 1250.1250 machine_max_acceleration_retracting = machine_max_acceleration_x = 1000.960 machine_max_acceleration_y = 1000,960 machine_max_acceleration_z = 1000,1000 machine_max_feedrate_e = 120,120 machine_max_feedrate_x = 200,100 machine_max_feedrate_y = 200.100 machine_max_feedrate_z = 12.12 machine_max_jerk_e = 1.5, 1.5 machine_max_jerk_x = 8.8 machine_max_jerk_y = 8.8 machine_max_jerk_z = 0.4, 0.4 machine_min_extruding_rate = 0.0 machine_min_traveLrate = 0.25 max_hefan = 0.0 max_print_height = 210 max_print_speed = 200 max_volumetric_speed = 0 min_fan_speed = 30 min_layer_height = 0.07 min_print_speed = 15 min_skirt_length = 4 notes = nozzle_diameter printer = 0.4 only_retract_when_crossing_perimeters = 800_retract_when_crossing_perimeters = 0 remaining_retract_prevention = 92_retract_processing = 800_perfore_revention = MK_0oze_prevention = 800_perfore_processing = 800_perfore_revention = 800_performance_revention = 0 resolution_positions = 1 remaining_prevention = MK0ze_prevention = 1 = 1 retract_before_wipe = 0% retract_layer_change = 1 retract_length = 0 retract_length_toolchange = 4 retract_lift = 0.6 retract_lift_above = 0 retractJifLbelow = 209 retract_restart_extra = 0 retract_restart_extra = 0 retract_restart_extra skirt_toolistance_material = single_exrestart_extra = 0 retract_restart_extra skirt_toolistance_material = 0 single_extrode_extra skirt_toolistance_material = 0 retract_restart_extra skirt_toolistance_material = 0 single_extrode_speed = 1 silent skirt_toolistance_change = 0 single_extrode_speed = 1 1 slowdown_below_layer_time = 20 spiral_vase = 0 standby_temperature_delta = -5 temperature = 250 threads = 4 toolchange_gcode = travel_speed = 180 use_firmware_retraction = 0 use_relative_e_distances = 1 use_volumetric_e variablejayer_height = 0 = 1 = 0 wipe wipe_tower wipe_tower_bridging = 1 = 10 = 0 wipe_tower_rotation_angle wipe_tower_width wipe_tower_x = 60 = 170 = 125 wipe_tower_y wiping_volumes_extruders = 70.70 wiping_volumes_matrix = 0 = 0 z_offset clip_multipart_objects dont_support_bridges = 1 = 1 = 0 elefant_foot_compensation extrusion_width = 12:45 first _layer_height = 0.2 infill_only_where_needed = 0 interface_shells = 0 layer_height = 0.2 raft_layers = 0 seam_position = nearest slice_closing_radius = 0.049 support_material = 0 support_material_angle = 0 support_material_auto = 1 support_material_buildplate_only = 0 support_material_contact_distance = 0.1 support_material_enforceJayers = 0 support_material_extruder = 0 support_material_extrusion_width = 00:35 support_materialJnterface_contact_loops = 0 support_material_interface_extruder = 0 support_material_interfaceJayers = 2 support_materialJnterface_spacing = 0.2 support_material_interface_speed = 100% support_material_ pattern = rectilinear support_material_spacing = 2 support_material_speed = 5 support_material_synchronize_layers = 0 support_material_threshold = 55 support_material_with_sheath = 0 support_material_xy_spacing = 50% wipe_into_objects = 0 xy_size_compensation = 0 bottom_fill_pattern = rectilinear bottom_solid_layers = 3 bridge_angle = 0 bridge_flow_ratio = 0.95 bridge_speed = 5 ensure_vertical_shell_thickness = 1 external_perimeter_extrusion_width = 00:45 external_perimeter_speed = 5 external_perimeters_first = 0 extra_perimeters = 0 fill_angle = 45 fill_density = 0% FillPattern = grid gap_fill_speed = 40 infill_every_layers = 1 infilLextruder = 1 infill_extrusion_width = 0.45 infilLoverlap = 40% infilLspeed = 10 overhangs = 0 perimeter_extruder = 1 perimeter_extrusion_width = 0.45 perimeter_speed = 5

Perimeters = 1 small_perimeter_speed = 5 solid_infill_below_area = 0 solidJnfilLeveryJayers = 0 solidJnfilLextruder = 1 solidJnfill_extrusion_width = 0.45 solidJnfilLspeed = 10 thin_walls = 1 to p_f i I Lpatte rn = rectilinear top_infillsettings = 50 topjnfils = 0.4 mm width = 50 topjnfils = 0.4 nlay width = 0.4nlay_nt PC48 CUP filament_settings_id = "PC48240_100_NOFAN" printer_settings_id = Original Prusa i3 MK30.4mm NORETRACT printer_model = MK3 printer_variant = 0.4 FIG. 3 shows a perspective view of the cup 300 produced in this way. As a thermal stress test, the cup was filled with water 302 at a temperature of at least 95 ° C. and visually examined for changes in shape. For comparison, a cup of the same shape was made from polylactides (PLA) (not shown in more detail) and also filled with water at a temperature of at least 95 ° C. In the case of the cup made from PC48, no change in shape could be detected with the naked eye after filling with the water. In contrast, the cup made of PLA has deformed significantly. This shows that the PC-48 material is more thermally robust compared to PLA.

Claims

Expectations

1. Process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III)

Y ¹ - (CH ₂ ) _C -Y ²

(II)

, where Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) - group or -C (= 0) -0-R group and OH group, where R is a hydrogen atom or a C1 Is -C10 alkyl group; and the index c is an integer from the range 8 to 200,

Y ¹ - [(CH ₂ ) aX-] mY ²

(IN)

, where Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) -0- group and -0-C (= 0) -0-R-group, R-0-C (= 0) group or -C (= 0) -0-R group and OH group, where R is a hydrogen atom or a C1-C10-alkyl group; X for each of the m repeating units is independently selected from C (= 0) -0- group or -O- C (= 0) -group and-0-C (= 0) -0- group, where X is in the last Repeating unit of formula (III) is not present; a is an integer from the range from 8 to 200, where a is the same or different for each of the m repeating units; and the subscript m is an integer from the range 2 to 40; wherein the method comprises: i) producing an alcoholic and / or aqueous mixture of a polyethylene-like polymer comprising methylene groups and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group; ii) heating the mixture provided according to i) to a temperature in the range from 20 to 400 ° C .; iii) Separating the monomers of the general formula (II) and / or oligomers of the general formula (III) from or from the alcoholic and / or aqueous mixture obtained according to ii).

2. The method according to claim 1, further comprising: iv) optional purification of the monomers of the general formula (II) and / or oligomers of the general formula (III) obtained in accordance with iii); v) Repolymerization of the monomers of the general formula (II) and / or oligomers of the general formula (III) obtained according to iii) or iv) to give a polymer.

3. A process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) according to one of claims 1 or 2, wherein the polyethylene-like polymer comprising methylene groups and at least one functional group selected from 0-C ( = 0) group and 0-C (= 0) -0 group has a repeating unit of the general formula (I)

[-X- (CH ₂ ) _a -]

(I)

, whereby

X is selected from C (= 0) -0- group or -0-C (= 0) -group and-0-C (= 0) -0- group; a is an integer from 8 to 200.

4. A process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) according to any one of claims 1 to 3, wherein the alcohol is selected from the group of monofunctional or polyfunctional C1-C10 alcohols and their Mixtures, the alcoholic mixture of the polyethylene-like polymer according to i) having a water content in the range from 0 to 5% by weight based on the total weight of the alcoholic mixture; or where water is used to produce the mixture according to (i).

5. A process for the preparation of monomers of the general formula (II) and / or oligomers of the general formula (III) according to any one of claims 1 to 4, wherein the alcoholic and / or aqueous solution obtained in ii) comprises a mixture comprising monomers of the general formula ( II) and / or oligomers of the general formula (III) furthermore comprises monomers of the general formula (IV)

R ¹ -0-C (= 0) -0-R ²

(iv) where

R ¹ , R ^{2 are} each C1-C10 alkyl groups.

6. Composition comprising a monomer of the general formula (II) and / or an oligomer of the general formula (III)

Y ¹ - (CH ₂ ) CY ²

(II) where Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) group or -C (= 0) -0-R group and OH group, where R is a hydrogen atom or is a C1-C10 alkyl group; and the index c is an integer from the range 8 to 200, Y ¹ - [(CH ₂ ) aX-] mY ²

(III) where

Y ¹ and Y ^{2 are} each independently selected from R-0-C (= 0) -0-group or -0-C (= 0) -0-R-group, R-0-C (= 0) -Group or -C (= 0) -0-R group and OH group, where R is a hydrogen atom or a C1-C10-alkyl group; X for each of the m repeating units is independently selected from C (= 0) -0-group or -0-C (= 0) -group and-0-C (= 0) -0-group; a is an integer from the range from 8 to 200, where a is the same or different for each of the m repeating units; and the subscript m is an integer from the range 2 to 40; obtained or obtainable by a process according to any one of claims 1 to 5.

7. Use of the composition according to claim 6 for the production of polymers, in particular polyethylene-like polymers comprising methylene groups and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0- group, wherein preferably 90 to 99.5 mol%, more preferably 92 to 98 mol%, of the polyethylene-like polymer consist of methylene units (CH2).

8. A method for producing a finished part, comprising providing a material which has a polyethylene-like polymer, the polyethylene-like polymer having methylene groups (CH2) and at least one functional group selected from O- C (= 0) group and 0- C (= 0) -0 group includes, and archetypes of the material.

9. The method according to the preceding claim, wherein the primary shaping of the material comprises thermal primary shaping, wherein the primary shaping is preferably at least one method selected from the group consisting of: injection molding, extrusion, calendering, rotational molding, injection blow molding.

10. A method for producing a finished part from a material, the material comprising a polyethylene-like polymer, the polyethylene-like polymer having methylene groups (CH2) and at least one functional group selected from O- C (= 0) group and 0- C (= 0) -0 group and has a repeating unit of the general formula (I)

[-X- (CH ₂ ) aj

(I)

, whereby

X is selected from C (= 0) -0- group or -0-C (= 0) -group and-0-C (= 0) -0- group; a is an integer from 8 to 200, wherein the finished part is manufactured by means of an additive manufacturing process.

11. The method according to the preceding claim, wherein the material is provided as a filament and / or wherein the additive manufacturing process is 3-D printing.

12. Polyethylene-like polymer comprising methylene groups (CH2) and at least one functional group selected from 0-C (= 0) group and 0-C (= 0) -0 group, the polyethylene-like polymer having a number average molecular weight ( M _n ) in the range from 20,000 to 10,000,000 g / mol.

13. The polyethylene-like polymer according to claim 12, wherein 90 to 99.5 mol% of the polyethylene-like polymer consists of methylene units (CFI2).

14. Polyethylene-like polymer according to claim 12 or 13, comprising a

Repeating unit of the general formula (I)

[-X- (CH ₂ ) _a -]

(I) where